Abstract: Analysis of 25 regional rainstorm in Anhui Huaibei area from May to September during 1960- 2010 showed that: Huaibei regional rainstorm flood time evolution had‘early July to late August’feature. The EOF analysis found that features the regional rainstorm in Huaibei large scale circulation were two ridges and two grooves. The rainstorm area is located in the south side of the entrance of the upper westerly jet and low-level vortex convergence center southeast side, closed the meridional vertical circulation ascending branch. The cold air from high layer and the upper cold air intrusion, with high value of potential vorticity column form downward intrusion. The rainstorm area is located in the center of the vertical velocity and moist potential vorticity negative center north, vertical direction is moist potential vorticity positive and negative overlapping situation, and the low layer baroclinic convective instability and the high-level unstably combined, enhanced the atmospheric instability is proved to be a major cause of regional rainstorm in Huaibei.